Recovery of crude petroleum from plural strata by hot fluid drive



Jan. 26, 1965 C. PRYOR RECOVERY 0F' CRUDE PETROLEUM FROM PLURAL STRATA BY HOT FLUID DRIVE Filed June l5. 1961 INVENTOR RC. PRYOR l. .O2 m...

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A 7' TORNEKS United States Patent Oiitice 3,167,120 Patented Jan. 26, 196,5`

3,167,120 RECVERY F CRUBE PETRQLEUM FRM PLURAL STRA'EA BY HT FLUZID BREVE Robert C. Pryor, Bartlesville, Okla., assignor to Philiips Petroleum Company, a corporation of Delaware Filed June 15, 1961, Ser. No. 117,347 11 Claims. (Cl. 1166-40) jection wells. In the first case, wells 12 and '14 represent production wells in the ring; and in the second case, wells 12 and 14 represent wells in two lines of production wells parallel to and on each side of the line of injection wells 10. Well 10 is provided with casing 16 and tubing 18, while `wells 12 and 14 are provided with casing 20 and tubing 22. The wells extend thru a permeable water zone or stratum 24 lying adjacent a `stratum 26 containing heavy crude and separated from stratum 24 by impermeable shale 28. Strata 30, 32,

and 34 also contain heavy. crude and are separated by'imor loosely consolidated) separated by relatively thin imi permeable shale layers. Permeable water-bearing sands exist in both the upper and lower Oficina sections. The crude is so viscous that it is not readily amenable to conventional water flooding or fluid drive with reasonably spaced wells. This invention is concerned with a process for the production of crude oil from such an environment.

Accordingly, it is an object of the invention to provide an improved process for producing crudes of extremely low A.P.I. gravity. Another object is to provide an improved method of producing heavy crude by fluid drive. A further object is to eliminate pumping and the use of down-hole equipment involving moving parts. It is `also an object of the invention to increase the recovery of crude in primary production in the production of crude. Other objects of the invention will become` apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises passing a hot fluid, such as superheated H2O, thru a permeable stratum free of oil and lying adjacent a permeable oilbearing stratum but separated therefrom by an impermeable barrier, so as to heat the oil-bearing stratum (and its oils) to an elevated temperature which greatly reduces the viscosity of the crude oil; and, while the crude tions 42.

oil is in heated condition, forcing a fluid flushing or displacing agent thru the oil-bearing stratum to force the oil into a production well from which it is produced in conventional manner. A preferred embodiment of the process utilizes superheated water or steam as the uid for liooding the permeable stratum adjacent the oilbearing stratum. The use of superheated water or steam as the oil-driving uid is also preferred. By utilizing heated Water at a temperature of about 540 F., Monagas crude is lowered in viscosity so that it has the viscosity of Water used in the waterdrive. This preheating of the crude renders it readily producible by hot water or steam drive without resorting to extremely close well spacing. Hot gases such as air, combustion gases, etc., may be used to supply the heat for the first preheat.

In practicing the invention, the temperature of the preheating uid used to flood the permeable oil-free stratum ranges from about 300 to 750 F., depending upon the character of the crude to be produced. The temperature of the preheated crude should be high enough to lower its viscosity to that of water. The pressure applied to the Water or steam is dependent upon the temperature to be attained.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing which is an elevation in partial cross section of an arrangement of wells in a formation to which the invention is adapted.

Referring to the drawing, injection well 10 represents either a central injection well of a conventional 5, 7, or 9-spot well pattern, or an injection well in a line of inpermeable shale 36, 38, and 40.

The casing 16 of injection Well 10 is perforated at 42 and corresponding perforations are made in casing 20 of the production wells. Hot fluid such as superheated water or steam is injected thru tubing 18 so that it lloods stratum 24 and drives out water therefrom into production wells 12 and 14. The flooding of stratum 24 is continued for at least several cycles, one cycle being delined as the completion of flow of a body of ushing fluid from tubing 18 thru the stratum to tubing 22. With normal well spacing,`a flooding cycle extends over a period of at least a month. During an extensive period of several cycles, the adjacent oil-bearing `stratum 26 is heated to a temperature approaching the temperature of the flooded stratum and is then ready for production by fluid drive or displacement. e

During the injection of Huid thru stratum 24, packer 44 around tubing 18 is utilized to conline the injected tiuid to the desired section of well 10 adjacent perfora- It is necessary to pack olf the section of well 10 adjacent stratum 26 in order to produce this stratum. This is done by inserting packer 46 in casing 16 at the level of impermeable shale 36 and placing tubing 18 so that its lower end is at 48, and either inserting an imperforate packer in lieu of packer 44 or plugging perforations 42. Perforations 50 are produced in casing 16 and in casing 20. Hot flushing fluid, preferably, superheated water at a temperature of at least 500 F., or superheated steam, is injected thru tubing 18 and into heavy crudebearing stratum 26 while in preheated condition and the crude flows into wells 20 from which it is produced thru tubing 22 by the pressure of the injected hot lluid.

Shale zone 36 separating oil bearing strata 26 and 30 is relatively thin and heat is transmitted therethru during the production of stratum 26, thereby heating the crude in stratum 30. In order to provide adequate preheating of crude in stratum 30, uthe injection of ushing fluid thru stratum 26 may be continued for several cycles. After adequately preheating stratum 30, the sections of casings 16 and 20 adjacent this stratum are packed olf ina manner similar to the packing olf of the section of well adjacent stratum 26, andcasings 16 and 20 are perforated at S2 to provide a complete passageway for the injected and produced fluids.

Strata 32 and 34 are produced successively in the same or similar manner to the production of crude from strata 26 and 30. This necessitates perforation of the casings at 54 and S6 as shown in the drawing. It is desirable to pack off the ysection of wells 12 and 1.4 being flooded and produced, in the same manner as well 10, although this is not absolutely essential.

In the South Monagas lield of Venezuela, the permeable water zone 24 is about 10 feet in thickness and has a porosity of about 30%. Utilizing a 57-acre well spacing and a 5spot well pattern, the injection of 25,000 barrels per day (B PD.) of Water superheated to 540 F. .thru the center well is continued thru 6 cycles covering a period of about one year. The adjacent oil-bearing stratum (stratum 26) of about 20 to 30 feet in thickness is preheated during this period to a temperature just below the injection temperature. As the temperature of the 3 crude in stratum 26 rises during the preheating period, oil begins to flow into the 'production wells thru perfo-'rations 50 and is produced along with the water or steam during the preheating period. The injected water forms a pancake of hot water surrounding the injection well and lying under the oil-bearing stratum to be preheated.

At the end of 6 cycles of injecting superlieated water, injection is shiftedto the preheated'oillsand 26 and is maintained at the Isame rate of 25,000 B.P.D. and substantially at the temperature of 540 F. previously utilized.. At this rate of injection into the 20 to 30 foot thickness of oil stratum, only 2 or 3 cycles per year of circulation are effected. During the second year the hot water n ushing produces between 70 and 80 percent of the oil in the stratum being produced. l

During the production of oil fromvstratum 26, heat is transferred thru impermeable shale 36 into oil sand 30 so as to raise the temperature of the heavy crude therein. In the event the cr'ude in the upper area of stratum 30 is not raised sufficiently in temperature to render it easily p rod'ucible by hot water' flushing or steam ilushing at the end of the second year with 2 to 3 cycles of circulation thru stratum 26, injection of superheated water is continued for additional cycles until the desired amount of preheating is effected in stratum 30. Stratum 30 is produced by the same method as applied to stratum 26 when a desirable temperature has been reached therein. in this manner, additional strata are preheated and produced in succession until all of the oil-bearing strata in the structure are produced.

It is to be understood that'sections of wells 12 and 14 may be packed off adjacent the stratum being pro-duced as illustrated in connection with injection well 10. The injection pressure andthe hydrostatic head in the injection well produce substantially all of the oil in liquid form thru tubing 22 without the aid of pumping equipment. This eliminates the use of downhole pumps and is a distinct advantage in producing the formation illustrated.

The invention permits production of a 57 acre tract in the Monaga'seld with only 5 wells, whereas original production methods therein required 16 wells on this size tract and produced 10 to 20 percent of the crude as contrasted with 70-80 `pe'rcentproduced by the process of the invention'. Initial investment for the instant process is only vabout one-half of that required for producing by conventional methods. Actual acreage required for producing 12,000.B.P.D. of crude is reduced from 912 acres to 57 acres. Fuel for heating the water for the process is provided from the gas and waste oil-water emulsion from the process.

Certain modifications kof the invention will become apparent to those skilled in the art and lthe illustrative details disclosed are nott'o be construed as imposing unnecessary limitations 'on the invention.

We claim:

, 1. A process for producing hydrocarbons from a first permeable oil-bearing stratum, containing a viscous crude .difficult tov produce by fluid drive, which lies adjacent a second permeable stratum free ofhydroca-rbon material but separated therefrom by an impermeable barrier, said iirst and second permeable strata being penetrated by an injection well and by a production well, which comprises tlooding said second permeable stratum with hot H2O by injecting same thru one of said side wells into said second stratum and producing said H2O thru the other of said wells, thereby prehcating the adjacent iirst oil-bearing stratum; thereafter, while said first oil-bearing stratum is in preheated condition, injecting a hot fluid flushing agent under non-combustion conditions thru said injection Well into the preheated stratum so as to drive oil therefrom into said product-ion well, and recovering the produced oil from said production well.

2. The process of claim 1 wherein superheated hot water is injected as said H2O to preheat said oil-bearing stratum and as said ilushing agent.

3. The process of claim l using superh'eated steam as the flooding and flushing agents.

4. The process of claim 1 wherein a .third permeable oil-bearing stratum lying adjacent said first oil-bearing stratum, but separated therefrom by an impermeable barrier, is Ipreheated by the injected hot liushing agent, and said third stratum is produced while in preheated condition by injecting hot liushing agent into same thru said injection well and forcing same and heated o-il therein t'oward said production well.

5. The process of claim 4 using superheated water as the iloodingagent and as the ushing agent.

6. The process of claim 4 using superheated steam as the flooding agent and as the liushing agent.

7. The proceess of claim 1 wherein the injection temperature of said H2O is at least 300 F. and said oil is a heavy crude.

8. The process of claim 1 wherein water superheated under pressure to a temperature of at least 500 F. is injected as the flooding agent and as the iiushing agent.

9. The process of claim 1 wherein the ilooding is continued for at least several cycles with H2O at a temperature of at least 500 F. before ushing agent is injected into said li-rst stratum.

10. The process of claim 9 wherein Said iushing agent is also hot Water injected at a temperature of at least 500 F.

11. The process of claim 1 wherein the flooding is continued for at least several cycles with hot H2O before injecting said liushing agent; a third permeable-oil-bearing stratum lies adjacent said iirst permeable oil-bearing stratum and is penetrated by said wells; at least several cycles of hot H2O iiushing agent are applied to said rst oil-bearing stratum to produce same and to preheat said third oil-bearing stratum; and said third oil-bearing stratum is produced while in preheated condition by injecting hot H2O into same thru said injection well and driving same toward said production well.

References Cited in the iile of this patent UNITED STATES PATENTS 1,491,138 Hixon Apr. 22, 1924 2,561,639 Squires July 24, 1951 2,584,605 Merriam et al. Feb. 5, 1952 2,734,579 Elkins Feb. 14, 1956 2,801,090 Hoyer et al. July 30, 1957 2,954,218 Dew et al. Sept. 27, 1960 3,042,114 William July 3, 1962 3,097,690 Terwilliger et al. July 26, 1963 3,116,792 Purre Jan. 7,l 1964, 

1. A PROCESS FOR PRODUCING HYDROCARBONS FROM A FIRST PERMEABLE OIL-BEARING STRATUM, CONTAINING A VISCOUS CRUDE DIFFICULT TO PRODUCE BY FLUID DRIVE, WHICH LIES ADJACENT A SECOND PERMEABLE STRATUM FREE OF HYDROCARBON MATERIAL BUT SEPARATED THEREFROM BY AN IMPERMEABLE BARRIER, SAID FIRST AND SECOND PERMEABLE STRATA BEING PENETRATED BY AN INJECTION WELL AND BY A PRODUCTION WELL, WHICH COMPRISES FLOODING SAID SECOND PEARMEABLE STRATUM WITH HOT H2O BY INJECTING SAME THRU ONE OF SAID WELLS INTO SAID SECOND STRATUM AND PRODUCING SAID H2O THRU THE OTHER OF SAID WELLS, THEREBY PREHEATING THE ADJACENT FIRST OIL-BEARING STRATUM; THEREAFTER, WHILE SAID FIRST OIL-BEARING STRATUM IS IN PREHEATED CONDITION, INJECTING A HOG FLUID FLUSHING AGENT UNDER NON-COMBUSTION CONDITIONS THRU SAID INJECTION WELL INTO THE PREHEATED STRATUM SO AS TO DRIVE OIL THEREFROM INTO SAID PRODUCTION WELL, AND RECOVERING THE PRODUCED OIL FROM SAID PRODUCTION WELL. 